Beyond's opinion on the parents facebook page:
Take it all with a huge grain of salt. There are some pros but generally it is a lot of hand wringing about things that parents have no control over a usually don't understand.
Looking at the 2019 page, most of the parents that are on it now appear to be 2018 parents. They're a great resource for a lot of questions like "What is indoc like?" and "What is parents weekend all about" blah blah blah. In a lot of ways they are the experts on the subject because their kids have gone through the plebe thing more recently than anyone else has. The technical issues faced here are fresh in their minds and they know how to deal with them.
What the parents facebook pages are really bad at is dealing with new challenges that get thrown at midshipmen, like admirals getting fired and government shut downs. Parents, especially plebe parents lack the institutional memory to predict how things will play out. Some of the advice that gets dished out just kind of misses the mark, it's usually very genuine but unless you understand the present mechanics of KP you just don't have the experience to know how to tackle new issues. A lot of time the gouge about something is transmitted from a plebe, to a parent, who blasts it around the internet as fact. It is a game of telephone and words get twisted. Usually your son/daughter will know best, or will have an upperclassman they trust to seek out advice from.
The parents facebook should just be another tool for involvement in your kids experience. Just understand that everyone there has the same perspective, being a plebe parent and so the discussion there has a unique flavor.